Sterilizer



Feb. 6, 1940. R. E. BITNER 2,189,279

STERILIZER Fiied Jan. 25, 1937 2 Sheets-Sheet 1 RALPH E. BVTNEIZ.

\HVENTOR.

HES ATTORNEY.

Feb. 6, 1940. R. E. BITNER 2,189,279

STERILIZER Filed Jan. 25, 1957 2 Sheets-Sheet 2 QALPH E. BITNEQ INVENTOQ,

Patented Feb. 6, 1940 UNETED STATES PATENT GFFHfiE 6 Claims.

The present invention is directed to lamp structures for producing ultra violet light, for various applications.

More particularly, this invention relates to the treatment and sterilization of such liquids as are only slightly or not at all opaque to such rays, and it has for its object the construction and operation of apparatus for the purpose.

Sterilization apparatus employing ultra violet light sources has been successfully used for many years. The rays are usually generated by an are between two mercury electrodes in an evacuated quartz tube and the arc tube mounted in a larger quartz tube or receptacle around which the liquid is allowed to iiow. Because of the very high operating temperature of the mercury arc, the lamp itself must be separated some distance from the irradiated liquid.

Within the last few years it has been discovered that the intensity of the short ultra violet radiation and the current through the lamp do not vary proportionally with each other. As the current through the lamp is reduced the visible radiation falls on rapidly but the ultra violet diminishes at a much slower rate and when the power suppliedto the lamp has been reduced to a point where the lamp burns at an operating temperature of 100 F. the radiation is composed of 86% ultra violet and of this amount almost 90% is concentrated in the spectral region which has a wave length of 2537 Angstrom llllitS.

Ultra violet radiation of wavelength range between 2300 A. and 2900 A. is particularly destructive to all forms of germ life, especially those organisms found in water and for this reason such a radiator is ideal for a means of sterilization.

Changing the electrical operating conditions of the mercury arc lamp as noted above, in accordance with the present invention, reduces the operating temperature to such an extent that the arc tube may be immersed in the liquid to be sterilized, thus simplifying the structure and reducing its size and cost. This low temperature operation also permits the construction of a selfstarting lamp. A small quantity of argon or other inactive gas (from to 20 mm. of mercln'y pressure in the discharge tube produces) enough ionization to start the lamp without tipping and hence it may be used with alternating current, doing away with rotary converters and the associated apparatus generaly used when only alternating current power is available and the lamps operate only on direct current.

,5 Applicant has discovered that a suitable device for producing ultra violet light with the elimination of the conventional metallic electrodes inside the tube with the attendant lead-in wires sealed through the quartz wall. He discovered that the "electrod1ess type of tube is more 5 adaptable to this class of work, much cheaper to make, and lasts almost indefinitely. The socalled "electrodless tube derives its name from the fact that there are no electrodes inside the arc tube and no leading-in wires sealed through 10 the walls. The tube contains only a small drop of mercury and the chemically inactive gas to produce quick and easy ionization. The electrodes consist of metallic coverings around part of the tube, in close contact with the outside of 15 the quartz walls. In this position they form one plate of an electric condenser with the quartz acting as the dielectric and the gas molecules on the inside of the tube acting as the other plate. With proper circuit design and the use go of alternating current having a frequency of one mega-cycle per second or higher, this condenser electrode passes suflicient curent to properly light up the tube and at the same time cause only a small percentage drop in voltage.

Since the sterilization lamp is immersed in the liquid, it has been found advantageous to supply the electrical energy to one end only and allow the other end to be entirely free of connections and apparatus. Such a monopolar lamp may be inserted into a pipe line or thrust into a tank of liquid without danger of any electrical connections coming in contact with the liquid.

The electrical energy supplied to such a monopolar lamp is derived from a tesla or other coil and high frequency oscillator, the oscillator be .ing tuned to the resonant frequency of the coil. This type of circuit has been known to the art for many years and its theory and operation may 40 be found in the more advanced handbooks of electrical engineering.

Referring to the accompanying drawings constituting a part hereof, and in which like reference characters indicate like parts:

Fig. 1 is a vertical cross-sectional view of a device made in accordance with the present inventlon, some parts being .shown diagrammaticam; to

Fik. 2 is a cross-sectional view taken along the line 22 of Fig. 1;

Fig. 3 is a longitudinal cross-sectional view of a modified form of tube adapted for operation as described herein; and w Figs. 4 and 5 are similar views of still further modifications of such tubes.

The apparatus, when used as a sterilizer for liquids, comprises a conduit l0 having a T H and an inlet pipe l2 for the liquid, held in one of the branches of said T. The liquid flows through space M and in contact with tube l3 and out through pipe l3. The liquid thereby flows around all sides of tube i8 and flows substantially parallel to the same for most of the length thereof.

In the branch i 5 of the T H is a nipple l6 which holds the tube [8 in place. The tube consists generally of an envelope of quartz or other substance, wholly or partly transparent to ultra 'violet'light and is completely sealed and evac uated. Within the tube is a small amount of mercury and inactive gas, such as argon or the like. At the upper end of the tube is a metallic shell l9, roughly in the shape of the end of said tube, and said shell is secured in close contact with the tube by means of molten lead or a readily fusible alloy, which is poured into the space betwen the tube and shell and allowed to solidify. Because of the low temperature of operation of the device, a low melting point alloy is suitable for the purpose. The assembly is secured in nipple I6 by suitable insulating material which covers the shell and insulates it from the liquid. This may be sulphur which is melted and poured into place and allowed to solidify, to form a water tight joint.

The wire 24, which is connected to the metallic cap at the point 25, is run to the oscillator unit or circuit where it connects with the high voltage end of the coil 3 I. It has been found that an eflicient coil may be made by winding 500 turns of number 30 enamel wire on a Bakelite tube 1 /2 inches in diameter. When one end of such a coil is connected to an oscillating network at the point 32 and the system actuated so as to generate about two megacycles per second, the coil 3| will be in resonance and a very high voltage will be produced at the cap l9 which will cause the tube i8 to li ht up and emit the characteristic mercury radiation.

The oscillating network is a simple conventional form in which the three electrode vacuum tube 26 is supplied with plate current through the choke coil 34 and the positive terminal 353. The filament current enters at the terminal 35A, both plate and filament circuits having a common negative terminal 36. A condenser 33 allows the high frequency impulses to pass directly from the plate to the oscillating circuit which consists of an inductance 21 and a variable condenser 30. The variable condenser is usually necessary because difierent sizes 01' pipe and different lengths of quartz tubing l8 aflect the tuning of the coil 3|, hence the structure is completely assembled before the final tuning adjustment is made. After the liquid has started through the piping, the condenser 30 is adjusted for maximum brilliancy. Other forms of oscillating circuits may be used and a spark gap may replace the vacuum tube as a means of generating the high frequency current without departing from the theory of operation of the monopolar ultra violet light radiator.

Fig. 3 shows an improved form of monopolar lamp with the electrode 50 positioned along the central axis of the cylinder. The main body of the tube 4| is similar to the tube l6. However, in this form, a re-entrant tube 42 is sealed into the envelope and anchored by a quartz rod 43 to the extreme end point 44. At the other end a ring seal 48 is made, and an entrance tube is provided for, which is sealed oil at point 41 after the structure has been evacuated and mercury and the proper amount of. argon introduced. A quantity of conducting material, such as melted lead, is then poured into the re-entrant tube 42 where it solidifies and forms the external electrode 50. By placing the electrode in this position one is able to secure a greater active surface area and to provide a shorter arc length for the high frequency discharge which moms in the space 48.

In adapting the lamp of Fig. 3 to the structure shown in Fig. 1, an external cap electrode is not necessary. The wire 24 is soldered to the lead electrode at the point 45 and the whole mounted in a sulphur base.

Fig. 4 shows another form of lamp designed to be used with liquids which have high electrical conductivity, such as lemonade and the like. This lamp is constructed of two pieces of quartz tubing of different diameters, the larger piece 5| forming the outer surface of the lamp, and the smaller tube 52 forming the main arc tube. The inner piece is flanged at 53 and a ring seal made to the outside tube at 54. This leaves a central narrowed space 55 for the arc and provides a bulb-like extremity 56 where the mercury drops may condense when the lamp is in operation. At the other end of the lamp the tube 52 projects beyond tube 5| so that the space 51 extends beyond the outer shell. The outer tubing at this el 1 is bent inwardly at 65 and an external ring seal me "e at 66. The cylindrical cavity 64 is then fully exhausted and sealed ar the point 61. No gas of any kind s usually introduced into this cavity 64, which acts as an efiec tivle transparent heat insulator. The proper quantities of mercury and argon are introduced into tube "2 and it is sealed off at point 58. A shell 16' is formed on the end 5l thereof and is held in place by lead H or the like.

When the tube structure of Fig. 4 is mounted in a system as shown in Fig. 1, the only point of contact of the arc tube with the liquid is at the bulb 56. This results in the bulb 56 maintaining a temperature somewhat lower than the rest oi the arc space 55 and 51 and will therefore cause the mercury to condense in this portion and keep the walls of the rest of the tube clear and transparent. It has been found that when such a lamp is mounted in the structure shown in Fig. 1 and operated as described, an increase in brilliance is obtained when the terminal 36 is connected to the pipe l3, as by wire 31. This additional connection changes the lamp to a bipolar type, and the complete circuit may be traced as follows; from the oscillating circuit at the point 32, through coil 3| which acts as a step-up voltage transformer, to cap 10, through the quartz wall condenser to space 51, down the discharge tube 55, to bulb 56, through the quartz wall to the surrounding liquid in space [5, to pipe l3 and back to the oscillating generator through wire 31 and terminal 36.

It will be seen that the evacuated space 64 of Fig. 4 performs a number of functions; first it tends to keep the surface of the discharge tube 52 free from mercury condensation by providing a transparent heat insulation which keeps the main discharge space 55 at a higher temperature than the bulb 56; second, it provides a path for the electrical energy from the first electrode H to the second or virtual electrode at 56 free from leakage to the surrounding liquid; and third, it provides a constricted portion 55 relative to the end 58 which results in a more eflicient radiator.

The passage of high frequency electrical energy through the liquid in the space adiacent to the bulb 56 results in a sterilizing action quite difl'erent from the action of ultra-violet light. It has been found by investigation that liquids treated with such currents are sterilized in much the same manner as when the liquids are pasteurized, except that the high frequency currents operate at much lower temperatures. By using high frequency currents, beverages such as milk and beer may be sterilized at temperatures where the taste of the beverage is unafiected.

Applicant has found that the combination of ultra-violet light and high frequency currents applied at the same time, result in a sterilizing action greater than that obtained from the actions applied separately. It is not necessary that the liquid be conducting, since the capacity effect between the surrounding container pipe l3 and the gas in the bulb 56 is enough to pass large high frequency currents.

Fig. 5 shows a modified form of tube having an evacuated jacket completely surrounding the radiating surface. The re-entrant tube 17 contains the conducting material 18 as before and connection to the oscillator is made through the wire 19. The are discharge space is enclosed by the quartz envelope 8| which in turn is surrounded by the evacuated space 82 with its quartz envelope 83. Anchors at 84 and 85 serve to keep the unit rigid. A double ring seal 86 and 81 is employed to complete the tube. This type is purely a monopolar type of lamp since there is no return path for the electrical energy to flow from the lamp back to the oscillator circuit. Such a lamp is best adapted to the sterilization of liquids which are adversely influenced by the passage of high frequency electrical energy. The tube is encased in an insulator compound 88, which may be sulphur, which in turn is held by a pipe fitting nipple 89.

Although I have described my invention setting forth several specific embodiments thereof, it will be apparent to those skilled in the art that various changes and modifications may be made without departing from the spirit of the invention. For example, the tubes may be made of other material than quartz and the shape and form thereof may be substantially different from those illustrated in the drawings. The oscillating circuit may be of any known or desired type, it being merely essential that it produce high frequency, high voltage. The uses to which a device of this character may be applied are numerous and they are included in the present invention. These and other changes may be made in the details of construction and operation of my invention, which is to be broadly construed and to be limited only by the claims appended hereto.

What I claim is:

l. A sterilizer comprising a sealed envelope transparent to ultra-violet light, a substance capable of emitting ultra-violet light within said envelope, an external electrode in close proximity thereto, an evacuated annular jacket transparent to ultra-violet light surrounding the central portion of said sealed envelope, a source of high frequency electrical power, said power being electrically connected with said electrode, a conduit of conducting material, said envelope extending into same and electrically insulated therefrom and means for causing liquid to flow in said conduit in contact with said-envelope, said power being electrically connected with said conduit, whereby an electrical discharge takes place through said liquid.

2. A sterilizer comprising an elongated sealed envelope transparent to ultra-violet light, a. substance capable of emitting ultra-violet light within said envelope, an evacuated jacket transparent to ultra-violet light surrounding the central portion of said envelope, an exterior electrode sure rounding one end portion of said envelope, a conduit of conducting material, said envelope extending into same and electrically insulated therefrom, means for causing liquid to flow through said conduit in contact with said jacket and the other end portion of said envelope, and a source of high frequency electrical power connected between said conducting conduit and said external electrode.

3. A sterilizer comprising an elongated sealed envelope transparent to ultra-violet rays, 9. substance capable of emitting ultra-violet light within said envelope, a re-entrant tube closed at its interior end concentrically aligned with said envelope, said re-entrant tube containing conducting material thereby forming an electrode external to the confined volume of said sealed envelope, a conduit of conducting material, said envelope extending into same and electrically in sulated therefrom, means for causing liquid to flow in said conduit in contact with said envelope, a source of high frequency electrical power, said power being connected between said electrode and said conducting conduit, whereby an electrical discharge takes place through said sealed envelope and said liquid.

4. In a sterilizer of the class described, in combination, means for irradiating a liquid with ultra-violet rays and means for subjecting said liquid to the passage of high frequency currents; said former means comprising an elongated sealed envelope transparent to ultra-violet rays, a substance capable of emitting ultra-violet light within said envelope, an external electrode in close proximity thereto, an evacuated jacket transparent to ultra-violet light surrounding the central portion of said envelope, a conducting conduit, said envelope extending into same and electrically insulated therefrom, and means for causing liquid to flow in said conduit in contact with said envelope; and said latter means comprising a source of high frequency electrical power connected between said conducting conduit and said external electrode.

5. In a sterilizer of the class described, in combination, means for irradiating a liquid with ultra-violet rays and means for subjecting said liquid to the passage of high frequency currents; said former means comprising an elongated sealed envelope transparent to ultra-violet rays, a substance capable of emitting ultra-violet light within said envelope, an external electrode in close proximity thereto, an evacuated jacket transparent to ultra-violet light surrounding the central portion of said envelope, a conducting conduit, said envelope extending into same and electrically insulated therefrom; and said latter means comprising a. source of high frequency electrical power, one terminal of which is connected directly to said conducting conduit and the other terminal of which is connected through said transparent envelope to the free end of said tube, thereby forming a concentric electrode within said conducting conduit.

6. A sterilizer comprising an elongated sealed envelope transparent to ultra-violet light, a substance capable of emitting ultra-violet light within said envelope, a re-entrant tube closed at its interior end concentrically aligned with said envelope, said re-entrant tube containing conducting material thereby forming an electrode external to the confined volume-of said sealed envelope, an evacuated jacket transparent to ultraviolet light substantially surrounding said transparent envelope, a conduit of conducting material, said envelope extending into same and electrically insulated therefrom, means for causing liquid to flow in said conduit in contact with said jacket, a source of high frequency electrical power, said power being connected between said electrode and said conducting conduit, whereby an electrical discharge takes place through said sealed envelope and said liquid.

RALPH E. BITNER. 

